1. Field of the Invention
The present invention relates to an ink jet recording head, and more particularly to a recording head for generating ink droplets used in an ink jet recording system in which ink droplets are generated and deposited onto a record medium such as paper to make a record.
2. Description of the Prior Art
An ink jet recording system, in which ink droplets are generated and deposited onto a record medium such as paper to make a record, generates negligible noise when it is operated, allows high speed recording and can make the record on plain paper without special processing such as fixing. Various types of apparatus of this system have been vigorously developed.
A recording head of the ink jet recorder usually has an orifice through which ink is discharged, ink path connected to the orifice and including a portion in which an energy for discharging the ink acts on the ink, an ink reservoir for storing therein the ink to be supplied to the ink path and an ink supply hole through which the ink is supplied to the ink reservoir from externally of the recording head.
The energy for discharging the ink in the recording operation is created by an energy generating device such as a heat generating device or piezoelectric device arranged at a predetermined position in the portion of the ink path which applies the energy to the ink (energy acting portion).
Of the ink jet recording heads of this type, a recording head which can be mass-produced with a high precision is one in which a wall made of a photosensitive resin film which forms the ink path and the ink reservoir is formed on a substrate on which the ink discharge energy generating device is mounted, and a cover for the ink path and the ink reservoir is formed.
FIG. 1 shows major portions of a typical example of such prior art ink jet recording head. It is a perspective view of the prior art ink jet recording head.
Numeral 1 denotes an orifice through which liquid is discharged to form flying droplets, numeral 2 denotes an ink path connected to the orifice 1 and having a portion (not shown) in which a discharging energy generated by a discharging energy generating device 6 mounted on a substrate 5 acts on the ink, numeral 3 denotes an ink reservoir for supplying the ink to the ink path 2, numeral 4 denotes an ink supply hole through which the ink is supplied to the ink reservoir 3 from externally of the head, numeral 5 denotes the substrate on which the discharge energy generating devices 6 are mounted to face the ink paths 2, and numeral 7 denotes a cover.
A so-called full-multi recording head in which a plurality of orifices are arranged at a high density is suitable for high speed recording of a high resolution image. When the ink jet recording head shown in FIG. 1 is constructed as a full-multi recording head for high speed recording, refilling of the ink from externally of the recording head to the inside thereof is insufficient, and stable discharge of the ink and high response to a discharge signal are not attained.
Such shortcomings are considered to be due to the structure of the recording head. Since the ink path 2 and the ink reservoir 3 are formed in union, the depth of the ink reservoir 3 is equal to the depth of the ink path 2. Since the depth of the ink reservoir 3 is determined with the sizes of the ink path 2 and the orifice 1 dominating it, the capacity of the ink reservoir 3 is not sufficient enough to store the ink necessary to rapidly supply the ink to the plurality of ink paths 2.
In order to resolve the above structural problem, the ink path and the ink reservoir may be constructed to have sizes to satisfy their respective functions in order to form the ink reservoir with a sufficient capacity.
FIG. 2 shows a perspective view of a typical example of such a recording head.
In the recording head of FIG. 2, a wall made of photosensitive resin which forms the ink path 2 is formed on a substrate 5, a ceiling or cover 7 is overlayed to form the ink path 2, and the ink reservoir 3 made of ceramic, glass or resin is bonded. Accordingly, the ink path 2 and the ink reservoir 3 are constructed to be large enough to satisfy their respective functions and the shortage of the capacity of the ink reservoir 3 described above is resolved. However, in the recording head of this structure, since the ink reservoir 3 and the ink path 2 are separately formed and the ink reservoir 3 is bonded on the substrate 5 to form recording head, the number of steps increases and the experience of an expert and a long time are required in order to precisely position the ink reservoir 3 and prevent the ink path 2 from being clogged by the bond. Accordingly, it is difficult to mass produce such a recording head.